Description
   Override this function in a channel validator in order to apply a different
   version validation scheme.  An example of this use is in the PEAR_Validate_PECL
   class, which overrides validateVersion() to be less strict than
   the default PEAR_Validate::validateVersion().
  
   Errors should be reported using
   _addFailure()
   method, and non-fatal errors (warnings) should be reported using the
   _addWarning()
   method.